Just east of here, where the towering peaks of the Zagros mountains mark the border with Iran, a single product dominates the Iraqi exports hauled across the frontier by pack mule and tractor-trailer.
That product is liquor: from well-known Western brands of bourbon and Scotch whisky to various types of vodka, gin and anise-flavored arak.
Iraq's booming liquor trade with Iran is a consequence of the divergence between the two countries' laws. Alcohol is banned inside the Islamic Republic of Iran. It is legal in secular Iraq, even if most Iraqis avoid it for religious reasons.
Not only is liquor legal here, it is untaxed and cheap. Stores sell liter bottles of Johnny Walker Red Label for just US$10. In Iran, the same bottle commands at least five times the price, people here say.
"A tractor-trailer load of Jack Daniels is worth a few million dollars on the other side," said Staff Sergeant David Spence-Sales, 34, of the US Army's 101st Airborne Division. "It's illegal to bring alcohol into Iran but it's not illegal to ship it out of Iraq."
The penalty for sale or consumption of alcohol in Iran is a fine or flogging, or both.
Iranian citizens who are Armenian Christians are legally allowed to make their own wine for church services, as well as spirits for their own personal consumption.
Despite being outlawed, foreign alcoholic beverages have been found in Iran since the 1979 revolution -- from well-known labels to harsher contraband from nearby parts of the former Soviet Union.
The arbitrage keeps afloat a plethora of liquor stores in Sulaimaniyah, the largest city in the Kurdish lands of northeastern Iraq and a center of trade with Iran.
Spence-Sales, whose long-range surveillance unit has trained several groups of Iraqi border police, says Iraqi customs officers simply wave the trucks through the main border post near the town of Penjwin, despite knowing the trucks ferry goods prohibited across the line.
At least a few of the 100 to 200 trucks that cross into Iran at Penjwin each day are laden with liquor, said Sergeant Louis Gitlin, a member of the same Army unit. Across the border, truckers pay bribes to see the loads through Iranian customs.
"They'll pick a small border site and pay the Iranians US$20, and they'll leave it open all day," said Spence-Sales, a Canadian from Toronto. "It's big money over there."
"Everybody gets his little piece," Gitlin said.
At a staging point for pack trains near the border, a group of smugglers loaded crates of vodka, whiskey and gin onto a dozen pack horses destined for a rocky trail that leads into Iran.
The smugglers, all ethnic Kurds said the smuggling is made easier because Kurds, who dominate the population on both sides of the border, are able to move back and forth with ease.
Besides liquor, Iraqi exports to Iran include cigarettes, televisions, vacuum cleaners, scrap metal and heavy machinery, as well as subsistence food such as rice and beans, the soldiers said. But liquor is the most lucrative, Spence-Sales said.
Six US military surveillance units and 870 Iraqi border police officers -- most of them ex-Kurdish independence fighters -- patrol the 698km border between Iraqi Kurdistan and Iran.
Mule and horse trains have long plied the rocky mountain trails leading between the two countries, Spence-Sales said. The US military and its Iraqi allies keep an eye on the incoming trade, usually only checking travelers' documents and watching for Islamist fighters coming from Afghanistan, he said.